1. Field of the Invention
This invention relates generally to camera auxiliary lighting systems and, more particularly, to using auxiliary light sources for reduction of red-eye effects.
2. Description of the Related Art
In capturing images of a scene with a camera, such as producing photographic exposures or recording digital representations, it frequently is necessary to supplement ambient light in the scene with light from a high-energy auxiliary light source. A typical auxiliary light source is an electronic strobe, commonly referred to as a flash unit. A flash unit includes capacitors that store a relatively large electrical charge and then discharge it through a flash tube, such as a xenon flash bulb, that achieves fill illumination intensity very quickly. A shutter mechanism of the camera is operated while the flash unit capacitors are discharged, thereby capturing the illuminated scene on film or in digital storage. The supplemental illumination provides the increased ambient light level needed for a proper exposure. Automatic exposure systems on cameras with flash units can be designed so they sense when the ambient light level is not sufficient for a properly exposed image to be produced and automatically operate the flash unit with the shutter mechanism to achieve proper exposure.
When the ambient light level is sufficiently dark that supplemental illumination is necessary, it also is likely that the pupils of persons in the scene are dilated. Because the flash unit so quickly reaches its full brightness, the supplemental light can reflect into the eyes of the persons in the scene before their pupils can react to the bright supplemental illumination and close down, or constrict. As a result, the blood supply in the retinas of their eyes sometimes can be illuminated and visible in the captured image, resulting in an effect referred to as "red-eye". Such effects are very unnatural appearing and therefore many cameras with automatic exposure/flash systems are designed to avoid the red-eye effect. For example, some cameras locate the flash tube as far away as possible from the optical axis of the camera objective lens. This reduces the red-eye effect somewhat because the light illuminating the retina cannot reflect straight back into the objective lens and through the shutter to appear in the captured image. Rather, some of the light is reflected away from the optical axis of the camera lens.
Other cameras reduce red-eye with one or more secondary capacitors that discharge and illuminate a secondary light source, such as a halogen bulb, before the primary capacitors illuminate the primary light source (the flash unit). The secondary light source is not necessarily of sufficient brightness to provide correct exposure, but is of sufficient brightness so the pupils of persons in a scene will react to the secondary light and constrict. Thus, the secondary light provides an automatic "pre-flash" illumination that occurs sufficiently before the primary illumination to prevent the blood in the retinas of the eyes from being visible in the captured image, thereby reducing or eliminating the red-eye effect. Unfortunately, the extra capacitors and bulbs add to the cost, size, and weight of the camera and place added demands on the camera batteries.
Many compact cameras have multiple light sources that perform multiple indicating functions. For example, infrared light sources not visible to the human eye are often used for automatic ranging systems. Visible, red or white light sources are often used for pre-flash illumination. Often red-color lights are used for self-timer indication, low battery, and flash-ready lights. It is generally desirable to use a single light source to perform multiple functions, because this usually decreases cost, size, and weight of the camera and can reduce operational demands on the camera batteries. For example, U.S. Pat. No. 4,500,193 to Suzuki et al. describes a camera in which an under-exposure indication and a shutter release indication are provided by the same indicator light. Similarly, U.S. Pat. No. 4,272,176 to Maitani et al. describes a camera in which a battery check status and self-timer operation are both indicated by a single light source. The consolidation of light source functions has been extended to include red-eye reduction systems. For example, it is known to use the halogen bulb of a pre-flash red-eye reduction system to also indicate self-timer operation. When the flash unit must be activated for proper exposure under low light conditions, the red-eye reduction system is activated and the pre-flash illumination is provided. The full intensity supplemental illumination and shutter opening then takes place.
Combining the self-timer indicator light and red-eye reduction light together provides some consolidation of elements. Not all cameras, however, include self-timer systems. Moreover, cameras typically include a variety of other light sources. Maximum consolidation benefits, in terms of the numbers of light sources combined on any one camera and in terms of the number of cameras that would benefit, would be achieved if the light sources for more universally-installed systems and for additional functions could be combined with red-eye reduction light sources.
From the discussion above, it should be apparent that there is a need for red-eye reduction systems that combine the light source for the red-eye reduction system with the light source for other common camera systems, thereby achieving greater reduction of camera cost, size, and weight over the greatest number of cameras. The present invention fulfills this need.